Land-based or marine gas turbine engines frequently are derivatives of engines designed for best thermal efficiency operation in aircraft. The design predetermines such engine characteristics as pressure and volume ranges which define mass flow rates. The design also matches compressor and turbine operation to avoid the compressor approaching its stall condition. In the art, this is sometimes referred to as providing a "stall margin" and the operation of the compressor is designed to function along compressor operating lines.
Because such derivative gas turbine engines are marine or land-based, there exists a capability to enhance thermal efficiency and power output capability through the injection into the engine flow stream of an additional higher energy fluid, herein sometimes called steam, which has a specific heat at constant pressure (C.sub.p) greater than the C.sub.p of the normal operating fluid flowing through the engine. One arrangement for utilizing such a higher energy fluid injected into a gas turbine engine is described in co-pending application Ser. No. 604,670--Johnson, filed Apr. 27, 1984, and assigned to the assignee of the present invention. The disclosure of that application is hereby incorporated herein by reference. As described in that application, such higher energy fluid as steam can be obtained by utilizing the heat generated by the gas turbine engine to change water to steam. Alternatively, steam can be obtained from an external source, for example as excess process steam.